1. Field of the Invention
The present invention generally relates to high voltage miniature transformers and more particularly to use of magneto-electric (ME) laminate composites in such transformers.
2. Background Description
The magneto-electric effect is a polarization response to an applied magnetic field H, or conversely a spin response to an applied electric field E. Ferro-electromagnetic materials have been studied, such as BiFeO3 and Pb(Fe1/2Nb1/2)O3. However, to date no single phase material with a high inherent coupling between spin and polarization has yet to be found.
Magneto-electric behavior has also been studied as a composite effect in multi-phase systems consisting of both piezoelectric and magnetostrictive materials. Piezoelectric/magnetostrictive composites have been the topic of numerous investigations, both experimentally and analytically. Various composite connectivities of the two phases have been studied including: 3-3 (i.e., ceramic-ceramic particle composite; ceramic, rare earth iron alloys and polymer composites) and 2-2 (laminate composites). These studies have confirmed the existence of magneto-electric effects in composites. However, the magnitude of the coupling was low for both connectivities in these prior art investigations.
Analytical and experimental investigations have focused on laminate 2-2 type composites of piezoelectric/magnetostrictive bi-materials. It has been found that the bi-material laminate composites showed much strong magneto-electric (ME) effects when they were operated at resonance states [1-7]. However, there were no reports about power device applications of the resonance ME effect. Magneto-electric devices are needed in applications such as high-power sold-state devices. Such applications require high voltage gains and high output efficiencies. However, lack of good magneto-electric materials has hampered high power applications.